JavaScript is known as a
'client-side language' - it runs on the user's browser. It is also an
'interpreted' language, which means it does not need to be compiled.
PHP and ASP are
server-side languages, which mean they run on the server. Basically, when the browser requests the page, the server runs the PHP or ASP file on the server. It then sends back a normal HTML page to the browser, customised by the PHP. So, any browser can view a PHP file, but some browsers cannot handle JavaScript. Any modern browser should be able to handle it, though.
